Prior art round balers generally have a bale forming chamber defined by an apron comprising an array of side-by-side belts, transverse slats trained on chains, a plurality of rolls or a combination of these various elements, e.g., rolls and belts. Crop material, such as hay, is picked up from the ground, as the baler travels across the field, and is fed into a fixed or expandable chamber where it is rolled up to form a compact cylindrical hay package. While still inside the bale forming chamber in its compacted form, the outer surface of the package is wrapped with twine or web material, such as net, prior to ejecting the wrapped bale from the chamber onto the ground for subsequent handling.
Exemplary of prior art round balers of the general type mentioned above is the baler disclosed in U.S. Pat. No. 4,956,968 issued in the name of K. R. Underhill on Sep. 18, 1990. In this baler an apron consisting of a combination of rolls and belts is used for bale formatlon. The baler also includes a mechanism for supplying net to a dispensing assembly which in turn feeds the net material into the bale forming chamber for circumferentially wrapping a formed cylindrical package of crop material. The dispensing mechanism includes a net insertion arrangement having a grasping portion for pulling net from the supply mechanism and inserting the free edge, commonly referred to as the tail, into the chamber. Subsequent to wrapping, the net material is severed by a cutting device, comprising an assembly for thrusting a knife edge transversely through the path of the net while net tension is increased causing a severing action as the net is pulled against the knife edge. After the net material is severed, the completed round bale is ejected from the baler by lifting the tail gate which opens the chamber rearwardly and thereby permitting the bale to be discharged onto the ground behind the baler.
Various other cutting arrangements are known in the round baler art, as exemplified by the apparatus disclosed in U.S. Pat. No. 4,597,241, issued Jul. 1, 1986, wherein a pair of opposing knives are used to shear the web material. In another known arrangement a knife strikes an anvil to provide the severing function as depicted in U. S. Pat. No. 4,922,690, issued May 8, 1990. Still another prior art mechanism contemplates a knife that is projected into a recess on the opposite side of the web path to urge the web against a cutting abutment, as shown in U.S. Pat. No. 4,599,844.
In all of the arrangements noted above, regardless of the type of baler involved, it is important that the cutting function be properly coordinated with the other functions of the baler. Coordination is especially critical in balers where the cutting takes place in an area where other mechanisms are functional during different phases of the bale making process. For example, in the baler shown in U.S. Pat. No. 4,956,968 the dispensing mechanism projects through the cutting area during a portion of the time that net is being dispensed into the chamber during the wrapping function. Serious damage would result if the cutting and wrapping functions were initiated at the same time due to a simple malfunction of their respective control mechanisms, operator error, etc.
Another example illustrating the importance of coordination of the various functions is the situation where the cutting assembly commences its function before the net is properly presented for severing, regardless of whether other mechanisms are in the path of the knife. Among the problems presented by this situation would be a ragged uneven cut, cutting before the bale is completely wrapped, a missed cut leading to the necessity of manual intervention and a myriad of other problems that would arise due to the complexities of the sequential nature of the automated steps of the balers of concern.